CLICK HERE FOR A TABLE comparing the gametophytes and sporophytes of the
major extant divisions. The table is linked to each of the divisions pictured.

Plant cells have a cell wall, large central vacuole, and plasmodesmata.

Like other eukaryotes, plants have a nucleus, plasma membrane,
mitochondria, and other organelles, but plant cells differ from
animal, fungal, and protist cells in a number of important ways. The
most obvious difference is the presence of a cell wall which
surrounds each cell. It is composed primarily of cellulose, a
complex carbohydrate made from glucose. Cellulose provides
structural support while remaining flexible; flower petals, for
instance, are flexible but will snap if folded too far.

When plant cells divide, they must form a new cell wall between them, and this
is accomplished by the formation of a phragmoplast, a system of
microtubules oriented along the axis of cell division which
helps to guide the deposition of cellulose. This is also an important
difference from the "green algae", which produce a phycoplast
during mitosis, in which the microtubules lie perpendicular to
the axis of division. Only plants and
charophytes
divide their cells with the aid of a phragmoplast.

Neighboring cells in plants are connected across their cell walls by
extensions of the cells through pores called plasmodesmata. A
plasmodesma allows cells to transfer nutrients, water, and some
other diffusible materials without having to pass them across
membranes or other barriers. They are also important for
understanding how diseases spread through the tissues of a plant.

At maturity, most plant cells are filled with a single large
vacuole, such that the nucleus, plastids, and other organelles are all
close to the cell membrane. This can be seen in the picture at right. At
the far right is the nearly transparent nucleus, and clusters of plastids can
be seen toward the bottom and left. Those plastids which appear to be in the
"middle" of the cell are actually at the periphery; remember that there is a
cell wall toward you, and a wall on the far side of the cell, with the vacuole
filling most of the space in between.

The vacuole is a membrane-bound bag of fluid, containing ions, stored nutrients,
and waste materials. The storage of waste materials is a very important
function of the vacuole, since plants cannot excrete their wastes the way
animals do.
The vacuole also assists the cell in maintaining turgor
pressure. The high concentration of materials in the vacuole
causes water to diffuse into the cell, increasing its volume. Because
of the cell wall, however, the amount of space into which the cell can
expand is limited. The cell thus exerts outward pressure on its cell
wall, and when all cells are maintaining this pressure, the plant gains
rigidity. You can notice this by comparing crisp fresh celery with
celery that has sat around and grown limp. The old celery has lost
fluids, and is no longer rigid.

Plastids manufacture food through photosynthesis.

Plastids are perhaps the most important feature of plants, that
is, from the perspective of animals that live on land. The plastid is
an organelle which contains
chlorophyll.
The chlorophyll captures the energy of light, and makes it accessible
to the plant for photosynthesis. This provides the energy
plants use to manufacture sugars, which are then used as a fuel
source for continued growth. The sugars are often linked together
for easy storage into a complex carbohydrate called starch.
Without these sugars and starch, life on land as we know it would be
impossible, for there would be practically no food -- no grains, no
fruits, no vegetables. Another useful by-product of photosynthesis is
oxygen, though plants are not the most important producers of this
gas. Most of our oxygen comes from
phytoplankton
in the earth's oceans.